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Mon, 17 Nov 2025 17:33:33 -0800 (PST) Received: from seungjin-HP-ENVY-Desktop-TE02-0xxx.dartmouth.edu ([129.170.197.94]) by smtp.gmail.com with ESMTPSA id 6a1803df08f44-88286318333sm104928426d6.24.2025.11.17.17.33.32 (version=TLS1_3 cipher=TLS_AES_256_GCM_SHA384 bits=256/256); Mon, 17 Nov 2025 17:33:33 -0800 (PST) From: pip-izony To: Hin-Tak Leung Cc: Seungjin Bae , Kyungtae Kim , linux-wireless@vger.kernel.org, linux-kernel@vger.kernel.org Subject: [PATCH v3] rtl8187: Fix potential buffer underflow in rtl8187_rx_cb() Date: Mon, 17 Nov 2025 20:32:59 -0500 Message-ID: <20251118013258.1789949-2-eeodqql09@gmail.com> X-Mailer: git-send-email 2.43.0 In-Reply-To: References: Precedence: bulk X-Mailing-List: linux-kernel@vger.kernel.org List-Id: List-Subscribe: List-Unsubscribe: MIME-Version: 1.0 Content-Transfer-Encoding: quoted-printable Content-Type: text/plain; charset="utf-8" From: Seungjin Bae The rtl8187_rx_cb() calculates the rx descriptor header address by subtracting its size from the skb tail pointer. However, it does not validate if the received packet (skb->len from urb->actual_length) is large enough to contain this header. If a truncated packet is received, this will lead to a buffer underflow, reading memory before the start of the skb data area, and causing a kernel panic. Add length checks for both rtl8187 and rtl8187b descriptor headers before attempting to access them, dropping the packet cleanly if the check fails. Fixes: 6f7853f3cbe4 ("rtl8187: change rtl8187_dev.c to support RTL8187B (pa= rt 2)") Signed-off-by: Seungjin Bae --- v1 -> v2: Addressing feedback from Ping-Ke Shih v2 -> v3: Address coding style feedback from Markus Elfring .../wireless/realtek/rtl818x/rtl8187/dev.c | 27 +++++++++++++------ 1 file changed, 19 insertions(+), 8 deletions(-) diff --git a/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c b/drivers/n= et/wireless/realtek/rtl818x/rtl8187/dev.c index 0c5c66401daa..7aa2da0cd63c 100644 --- a/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c +++ b/drivers/net/wireless/realtek/rtl818x/rtl8187/dev.c @@ -338,14 +338,16 @@ static void rtl8187_rx_cb(struct urb *urb) spin_unlock_irqrestore(&priv->rx_queue.lock, f); skb_put(skb, urb->actual_length); =20 - if (unlikely(urb->status)) { - dev_kfree_skb_irq(skb); - return; - } + if (unlikely(urb->status)) + goto free_skb; =20 if (!priv->is_rtl8187b) { - struct rtl8187_rx_hdr *hdr =3D - (typeof(hdr))(skb_tail_pointer(skb) - sizeof(*hdr)); + struct rtl8187_rx_hdr *hdr; + + if (skb->len < sizeof(struct rtl8187_rx_hdr)) + goto free_skb; + + hdr =3D (typeof(hdr))(skb_tail_pointer(skb) - sizeof(*hdr)); flags =3D le32_to_cpu(hdr->flags); /* As with the RTL8187B below, the AGC is used to calculate * signal strength. In this case, the scaling @@ -355,8 +357,12 @@ static void rtl8187_rx_cb(struct urb *urb) rx_status.antenna =3D (hdr->signal >> 7) & 1; rx_status.mactime =3D le64_to_cpu(hdr->mac_time); } else { - struct rtl8187b_rx_hdr *hdr =3D - (typeof(hdr))(skb_tail_pointer(skb) - sizeof(*hdr)); + struct rtl8187b_rx_hdr *hdr; + + if (skb->len < sizeof(struct rtl8187b_rx_hdr)) + goto free_skb; + + hdr =3D (typeof(hdr))(skb_tail_pointer(skb) - sizeof(*hdr)); /* The Realtek datasheet for the RTL8187B shows that the RX * header contains the following quantities: signal quality, * RSSI, AGC, the received power in dB, and the measured SNR. @@ -409,6 +415,11 @@ static void rtl8187_rx_cb(struct urb *urb) skb_unlink(skb, &priv->rx_queue); dev_kfree_skb_irq(skb); } + return; + +free_skb: + dev_kfree_skb_irq(skb); + return; } =20 static int rtl8187_init_urbs(struct ieee80211_hw *dev) --=20 2.43.0